Soviet Union almost completely destroyed the Aral Sea, heavily polluted much of Siberia in the quest for resources, and contaminated much of the Pripyat Marshes with nuclear radiation through Chernobyl.China is one of the largest poluters in the world and often times puts america to shame, honestly the record of communist states on the environment is fucking horrible.
And that only took around 45 years (1945 is around when they started and they died in 1991).
China's even worse, considering they started going full industrial pollution in the early 1970s.